Financial promotions do not always meet requirements to be "clear, fair and not misleading;"

Increasingly complex structures are introducing new risks and conflicts of interest;

Provision funds, which platforms like RateSetter offer to cover a certain amount of investor losses, "introduce risks to investors that are not adequately disclosed and may not be sufficiently understood by investors;"

Wind-down plans, put in place to take care of loans in case firms go bust, are not adequate;

Some platforms client money handling standards are not up to scratch.

The watchdog says in its report: "While we have identified some issues about the investment-based crowdfunding market, most of our attention at this time is on issues in relation to loan-based crowdfunding."

Falling transparency and rising complexity among peer-to-peer lenders is a theme throughout the FCA's 48-page report. The watchdog writes at one point: "Firms' desire to maintain confidence in platforms has occasionally led to firms acting in a nontransparent manner, masking true loan performance and exposing investors to risks."

A spokesperson for RateSetter told Business Insider: "We provide more disclosure around our Provision Fund than any other platform, and are proud of its track record of ensuring that no individual investor has ever lost a penny on RateSetter, although of course this is not a guarantee for the future.

"We'll continue to work with the FCA to ensure that our Provision Fund works in the interests of our investors. We are happy that the FCA is applying rigorous standards to the whole industry: as a founding member of the P2P Finance Association, we have worked to set high levels of disclosure which are unmatched elsewhere in financial services."

As a result of its initial findings, the FCA is proposing tougher new rules, including more mandated risk disclosures, strengthening wind-down rules, and restrictions on cross-platform investments.

FCA CEO Andrew Bailey says in an emailed statement: "Our focus is ensuring that investor protections are appropriate for the risks in the crowdfunding sector while continuing to promote effective competition in the interests of consumers.

"Based on our findings to date, we believe it is necessary to strengthen investor protection in a number of areas. We plan to consult next year on new rules to address the issues we have identified."

Christine Farnish, chair of the P2PFA, the UK trade body for peer-to-peer lenders, says in an emailed statement: "The critical test for any review of this sort is whether the sector is, overall, delivering beneficial outcomes for investors and borrowers. It is not easy for a regulator to grapple with new market entrants, especially when they are disrupting traditional business models and challenging powerful incumbents.

"We trust that the critical consumer outcomes test - based on a balanced and evidence-based assessment of benefits and risks - will be applied as the Review moves forward."

Funding Circle's cofounder and UK managing director James Meekings says in an emailed statement: "We welcome the FCA's review and support the focus on investor protection. Platforms must fully disclose information about risk and returns which is why Funding Circle publishes performance data on every single loan. Investors have now lent £1.8 billion to small businesses through the Funding Circle platform, supporting the creation of 40,000 new jobs."